Arie Zigler received the Ph.D. degree in physics from the Hebrew University, Jerusalem, Israel, in 1978.,He has 30 years of experience in experimental physics in area of electro-optics, spectroscopy, high-power lasers, and plasma physics, interaction of high intesity ultra short pulse laser with matter.
Consulting to numerous companies in USA and Israel. Dr. Zigler has published over 250 scientific publications delivered numerous invited talks at scientific conferences and holds 12 patents.
Main Scientific Contributions:
Origin of K-alpha radiation in laser produced plasma. During his Ph.D work he has found that the origin of K-alpha radiation in laser produced plasma is due to the presence of hot electrons deviated from the thermal distribution (ref 4). This method is widely used today by many laser produced plasma labs for measuring fast electrons.
Spectroscopy of heavy highly ionized atoms. In later years his research was focussed on the study of spectra emitted by highly ionized heavy ions. In particular a complex spectra emitted by the heavy, highly ionized atoms were collected and analyzed by calculating the bound-bound emission from a local thermodynamic equilibrium plasma. The total transition array of a specific single-electron transition, including all possible contributing configurations, was described by only a small number of super-transition-arrays (STA’s). The method allows interpolating smoothly between the relatively simple average-atom (AA) results and the detailed configuration accounting that underlies the unresolved transition array method. It was shown that under certain plasma conditions the contributions of low-probability transitions can accumulate into an important component of the emission. In these cases, detailed configuration accounting is impractical. On the other hand, the detailed structure of the spectrum under such conditions is not described by the AA method. The application of the STA method is widely used for interpretation of laser-produced plasma experiments as well as of radiative properties of stellar plasmas. (see ref 9,12,14,17,23,30,31,37,39,43,57) . Some of the publications were highly cited (above 220).
Guiding of ultra high laser intensities by plasma channels – electron acceleration.
The next major contribution was development of ablative capillary discharges. This approach was used as X-ray laser medium (ref 46, 52, 54,62, 75 and 148). In parallel in 1996 these slow capillary discharges were used for demonstration of optical guiding of a high intensity, up to 1019W/cm2 laser pulses in a long (up to 25cm) cylindrical plasma capillary channel. Optical guiding in a curved plasma (radius of curvature = 10 cm) was also demonstrated. Results show guiding of many tens of vacuum diffraction lengths in both straight and curved channels, in agreement with theory and simulation. In 2000 these channels were proposed as medium for achieving multi-GeV electron energies in the laser wakefield accelerator (LWFA) since it is necessary to propagate an intense laser pulse long distances in plasma without disruption. It was shown that electron energies of similar to GeV in a plasma-channel LWFA can be achieved by using short pulses where the forward Raman and modulation nonlinearities tend to cancel. Further energy gain can be achieved by tapering the plasma density to reduce electron dephasing. It was also demonstrated that energy depletion can be overcome using multistage capillary discharges. More than 30 publications in the related subjects were published and widely cited, for example ref 88 was cited more than 200. In the recent years a modified version of the capillary discharge was used by other group for the experimental demonstration of electron acceleration above GeV.
Conversion of Electrostatic to Electromagnetic Waves by Super-luminous Ionization Fronts –Generation of THz radiation.
Another area of investigation was a new approach for generation of THz radiation.It was achieved by the conversion of static electric fields to electromagnetic radiation by the incidence of a superluminous ionization front on plasma. For extremely superluminous fronts, the radiation is close to the plasma frequency and is converted with efficiency of order unity. A proof-of-principle experiment was conducted using semiconductor plasma containing an alternately charged capacitor array. The process has important implications in astrophysical plasmas, such as supernova emission, and to laboratory development of compact, coherent, tunable radiation sources in the THz range. Tunable radiation in the range from 0.1 to a few THz by the interaction of a superluminous photoconducting front with an electrostatic 'frozen wave' configuration in a semiconductor is reported. The interaction converts the energy contained in the 'frozen wave' into THz radiation, whose frequency depends on the energy in the laser pulse creating the superluminous front and the wavelength of the static wave. Power scaling as a function of the electrostatic 'frozen wave' energy was obtained. The capability of the concept to act as a narrow or wideband, tunable and powerful THz source was demonstrated. Using THz source we have measured the dielectric properties and thickness of thin semiconductor epitaxy layers by the reflection of THz radiation from the surface of a two-layered semiconductor wafer. The reflection from two interfaces the electromagnetic pulse has a destructive interference at a specific wavelength dependent on the thickness of the outer layer and its dielectric function. Near that frequency the reflection coefficient has a significant drop. By extending the incident pulse spectrum to include this interference frequency, a measurement of the thickness was obtained together with a direct measurement of the carrier number density. By this technique epitaxy layers of thickness down to a few microns were characterized (ref 103,110,111,114,121,122,126).
Propagation of high laser intensities in atmosphere.
Propagation of high power femto-second laser pulses in the atmosphere has been observed to self-channel in air and to propagate as narrow light filaments over distances from several tens to several hundreds of meters. This propagation is the result of a dynamical equilibrium among many effects, including Kerr self-focusing, diffraction and plasma defocusing. For laser intensities of 5x1013 W/cm2 a plasma column with electron density of 1016 - 1017 cm-3 is created in the wake of the self-guided pulse. We have proposed a simple method that allows obtaining a single and highly stable filament, out of a high-power pulse which would otherwise generate a random multiple filamentation patterns. We also have demonstrated that the location of the initial air breakdown can be controlled by forming stable filamentary structures in air due to the replenishment phenomena. The developed control techniques produced very stable single or multiple filaments with an angular stability of 10-5rad. The ultra-short (femtosec) lasers can generate plasmas at desired locations and distances of several km in the atmosphere, the lifetime of the plasma plume is too short to be of interest because of limits in the pulse energy. The ultra-short (femtosec) lasers are not sufficiently powerful to initiate air breakdown at distances of several kilometers in the atmosphere. A new approach based on the use of a combination of ultra-short pulse laser and a long pulse laser was developed. The ultra-short pulse is deployed first to create ionized channel at desired location by multi-photon ionization. It is then followed by a long pulse that maintains the plasma channel at a controlled temperature level. This technique can generate plasma channels remotely at realistic timescales for the development of leader stroke with controlled characteristics of ionized filaments generated launched into the atmosphere with many applications, among which the two most spectacular are lightning control and laser-assisted water condensation. Ref. 142,153,162,167,168, 177. The works on laser filamentation are highly cited.
Proton acceleration
Laser powered acceleration of protons is considered to be a key technology in the development of compact source for hadron therapy of cancer. An advanced concept for proton acceleration based on the field enhancement by micro-structures was proposed ref 165,166 . The target exhibits an enhanced absorption of laser energy by snow deposited on Sapphire targets. Using modest level ultra short laser facility (<1018W/cm2) and snow deposited targets, my group has demonstrated production of 10MeV protons ref 173 and recently using more powerful system 25MeV ref 182. This points to an order of magnitude increase of the maximal proton energy (namely to 100MeV level) with high intensity lasers of 5∙1019 W/cm2). We also have shown that the scaling laws of the protons energy is similar to the TNSA-scheme, but shifted to lower laser energies. This pioneering work proved that protons can be accelerated by modest energy lasers, with all the important implications to possible future realizations.